Trench semiconductor device having multiple active trench depths and method

ABSTRACT

A method of forming a semiconductor device includes providing a region of semiconductor material comprising a major surface. A termination trench is provided extending from a first portion of the major surface into the region of semiconductor material to a first depth and has a first width. A first active trench is provided extending from a second portion of the major surface into the region of semiconductor material to a second depth and has a second width less than the first width. A second active trench is provided extending from a third portion of the major surface into the region of semiconductor material to a third depth and has a third width less than the first width. A first conductive material is provided adjoining a fourth portion of the major surface, which is configured as a Schottky barrier. The selected trench depth difference alone or in combination with other features provides a semiconductor device having improved performance characteristics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 14/640,242 filed on Mar. 6, 2015 and issued as U.S. Pat. No.10,431,699 on Oct. 1, 2019, which is hereby incorporated by reference.

BACKGROUND

The present invention relates, in general, to electronics and, moreparticularly, to semiconductor device structures and methods of formingsemiconductor devices.

A Schottky device is a type of semiconductor device that exhibits a lowforward voltage drop and a very fast switching action. The lower forwardvoltage drop translates into less energy wasted as heat, which providesimproved system efficiency and higher switching speed compared toconventional PN junction diodes. This makes Schottky devices moresuitable for applications requiring higher efficiency power management.Such applications include wireless/portable devices, boost convertersfor LCD/keypad backlighting, charge circuits as well as other smallsignal applications.

With demands to further improve battery life in these applications andothers, the market is requiring even higher efficiency devices, such asSchottky devices having lower power dissipation, higher power density,and smaller die size. However, related Schottky device designs have notprovided a viable solution to meet the higher efficiency requirement.The related devices have exhibited poor performance including, amongother things, higher than expected leakage current and higher thanexpected forward voltage drop. In addition, this poor performance hasmade it difficult to produce a device capable of meeting present andemerging industry requirements for unclamped inductive switching (UIS),electro-static discharge (ESD), and/or surge non-repetitive forwardcurrent (IFSM) performance.

Accordingly, it is desired to have a method for forming a higherefficiency Schottky device and a structure that exhibits, among otherthings, an improved tradeoff between a lower leakage and a lower forwardvoltage drop to provide lower power dissipation and higher power densityin a reduced die size. Additionally, it is also beneficial for themethod and structure to be cost effective and easy to integrate intopreexisting process flows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a partial cross-sectional view of an embodiment of asemiconductor device in accordance with the present invention;

FIGS. 2-14 illustrate partial cross-sectional views of the embodiment ofFIG. 1 at various successive stages of fabrication in accordance with anembodiment of the present invention;

FIG. 15 illustrates a partial cross-sectional view of another embodimentof a semiconductor device in accordance with the present invention; and

FIG. 16 illustrates a partial cross-sectional view of a furtherembodiment of a semiconductor device in accordance with the presentinvention.

For simplicity and clarity of the illustration, elements in the figuresare not necessarily drawn to scale, and the same reference numbers indifferent figures denote the same elements. Additionally, descriptionsand details of well-known steps and elements are omitted for simplicityof the description. As used herein, current-carrying electrode means anelement of a device that carries current through the device, such as asource or a drain of an MOS transistor, an emitter or a collector of abipolar transistor, or a cathode or anode of a diode, and a controlelectrode means an element of the device that controls current throughthe device, such as a gate of a MOS transistor or a base of a bipolartransistor. Although the devices are explained herein as certain N-typeregions and certain P-type regions, a person of ordinary skill in theart understands that the conductivity types can be reversed and are alsopossible in accordance with the present description. For clarity of thedrawings, certain regions of device structures, such as doped regions ordielectric regions, may be illustrated as having generally straight lineedges and precise angular corners. However, those skilled in the artunderstand that, due to the diffusion and activation of dopants orformation of layers, the edges of such regions generally may not bestraight lines and that the corners may not be precise angles.Furthermore, the term “major surface” when used in conjunction with asemiconductor region, wafer, or substrate means the surface of thesemiconductor region, wafer, or substrate that forms an interface withanother material, such as a dielectric, an insulator, a conductor, or apolycrystalline semiconductor. The major surface can have a topographythat changes in the x, y and z directions.

DETAILED DESCRIPTION OF THE DRAWINGS

In Schottky rectifiers that use trench structures and trench-MOS action,the trenches occupy an area in the active area or cell of the device.The area that they occupy is not used for conduction and instead isconsidered to be wasted active area space. Thus, it is desirable tominimize the size or width of the trenches in the active area to be assmall as feasible while at the same time maintaining desired breakdownvoltage characteristics and maintaining the integrity of dielectricmaterial provided within the active trenches.

In general, the present embodiments relate to a semiconductor device andmethod of forming the semiconductor device having termination and activetrenches in a Schottky rectifier configuration. A first active trenchhas a depth that is different than a second active trench. The firstactive trench also has a depth that is different than the terminationtrench. In one embodiment, the second active trench and the terminationtrench have approximately the same depth. This configuration enablestrench Schottky devices having thinner epitaxial layers and higherdopant concentrations for selected breakdown voltages. The configurationprovides, among other things, a device having reduced forward voltagedrop and reduced current leakage. In one embodiment, the first activetrench can be among a plurality of first active trenches interspersedamong a plurality of second active trenches.

In an embodiment of the method, a first removal step, such as an etchstep, is used to form both the first active trenches and terminationtrenches, and a second removal step is used to form the second activetrenches. The method provides different trench depths for activetrenches and the termination trenches. In accordance with the presentembodiments, any decrease in breakdown voltage drop is minimized througha combination of active region dopant concentration and thickness, andactive trench depth differences, width and pitch.

FIG. 1 illustrates an enlarged partial cross-sectional view of anelectronic device 10, a semiconductor device 10, Schottky diode device10, or trench Schottky rectifier 10 in accordance with one embodiment.In the present embodiment, device 10 includes a region of semiconductormaterial 11, which includes a major surface 18 and an opposing majorsurface 19. Region of semiconductor material 11 can include a bulksubstrate 12, such as an n-type silicon substrate having a resistivityranging from about 0.001 ohm-cm to about 0.005 ohm-cm. By way ofexample, substrate 12 can be doped with phosphorous, arsenic, orantimony.

Device 10 further includes a semiconductor layer 14, doped region 14, ordoped layer 14, which can be formed in, on, or overlying substrate 12.In one embodiment, semiconductor layer 14 can be an n-type conductivityregion or layer, and can be formed using epitaxial growth techniques,ion implantation and diffusion techniques, or other techniques known tothose of ordinary skill in the art. In one embodiment, semiconductorlayer 14 includes major surface 18 of region of semiconductor material11. In some embodiments, semiconductor layer 14 has a dopantconcentration less than the dopant concentration of substrate 12. Aswill be described in more detail later, the dopant concentration and/ordopant profile of semiconductor layer 14 is selected in combination withother features of the present embodiment to provide a desired breakdownvoltage and a reduced forward voltage drop compared to related devices.It is understood that region of semiconductor material 11, semiconductorsubstrate 12, and/or semiconductor layer 14 can include other types ofmaterials including, but not limited to, heterojunction semiconductormaterials, and semiconductor substrate 12 and semiconductor layer 14 caneach include different materials. Such materials can include SiGe,SiGeC, SiC, GaN, AlGaN, and other similar materials as known to those ofordinary skill in the art.

In accordance with the present embodiment, device 10 includes a firsttrench 21 or termination trench 21 and second trenches 23 or activetrenches 23. In one embodiment, termination trench 21 extends from majorsurface 18 into semiconductor layer 14 towards semiconductor substrate12. In some embodiments, termination trench 21 can extend intosemiconductor substrate 12. In other embodiments, termination trench 21can terminate within semiconductor layer 14 thereby leaving a portion ofsemiconductor layer 14 disposed between a lower extent of terminationtrench 21 and semiconductor substrate 12. In one embodiment, terminationtrench 21 includes a dielectric layer 212, a dielectric region 212, or adielectric structure 212 disposed adjoining sidewall and lower surfacesof termination trench 21 as generally illustrated in FIG. 1.

In accordance with the present embodiment, dielectric layer 212 definesa lower surface 210 of termination trench 21 at a depth 216 from majorsurface 18. It is understood that lower surface 210 may not be flat, butmay have other shapes including, but not limited to curved, rounded,partially-curved, or partially-rounded shapes. In accordance with oneembodiment, depth 216 corresponds to the lowest extent of lower surface210 from major surface 18. In one embodiment, dielectric layer 212 canbe a thermal oxide having a thickness in a range from approximately 0.05microns to approximately 0.5 microns. In other embodiments, dielectriclayer 212 can be other types of oxides, nitrides, combinations thereof,or other materials known to those of ordinary skill in the art.

In one embodiment, termination trench 21 further includes one or moreconductive spacers 217 along sidewall surfaces adjoining dielectriclayer 212. In one embodiment, conductive spacers 217 can be a conductivepolycrystalline material, such as a doped polysilicon. In oneembodiment, a dielectric layer 219, a dielectric region 219, or adielectric structure 219 is disposed within termination trench 21. Inone embodiment, dielectric layer 219 can be further disposed on oradjacent a portion of major surface 18 spaced away from active trenches23 as generally illustrated in FIG. 1. In one embodiment, dielectriclayer 219 can be a deposited dielectric material, such as a depositedoxide, a deposited nitride, combinations thereof, or other dielectricmaterials as known to those of ordinary skill in the art. In accordancewith the present embodiment, dielectric layer 219 can be an oxidedeposited using a tetra-ethyl-ortho-silicate (“TEOS”) source usingplasma-enhanced chemical vapor deposition (“PECVD”) or low pressurechemical vapor deposition (“LPCVD”), and can have a thickness in a rangefrom approximately 0.2 microns to approximately 1.0 micron. In someembodiments, termination trench 21 can have a width in a range fromapproximately 4 microns to approximately 20 microns. In one embodiment,termination trench 21 can have a width of approximately 10 microns.

In accordance with the present embodiment, device 10 includes activetrenches 23 and active trenches 24 extending from major surface 18 intosemiconductor layer 14 towards semiconductor substrate 12. In oneembodiment, active trenches 23 include a dielectric layer 222, adielectric layer 222, a dielectric region 222, or a dielectric structure222 disposed adjoining sidewall and lower surfaces of active trenches23. In one embodiment, active trenches 24 include a dielectric layer221, a dielectric region 221, or a dielectric structure 221 disposedadjoining sidewall and lower surfaces of active trenches 24. Inaccordance with the present embodiment, dielectric layer 222 defines alower surface 230 of active trenches 23 at a depth 226 from majorsurface 18 and dielectric layer 221 defines a lower surface 240 ofactive trenches 24 at a depth 224 from major surface 18. It isunderstood that lower surfaces 230 and 240 may not be flat, but can haveother shapes including, but not limited to curved, rounded,partially-curved, or partially-rounded shapes. In accordance with oneembodiment, depth 226 corresponds to the lowest extent of lower surface230 from major surface 18, and depth 224 corresponds to the lowestextent of lower surface 240 from major surface 18. In accordance withthe present embodiment, depths 226 and 224 are different from each otherand depth 226 is different than depth 216 of termination trench 21. Inone embodiment, depths 224 and 216 are substantially the same depth. Inone embodiment, dielectric layers 221 and 222 comprise a thermal oxidehaving a thickness in a range from approximately 0.05 microns toapproximately 0.6 microns. In some embodiments, dielectric layer 212 anddielectric layers 221 and 222 can be the same material. In someembodiments, dielectric layer 212 and dielectric layer 221 can be formedduring the same process step. In accordance with the present embodiment,dielectric layer 222 can be a different material than dielectric layer221 and/or can have a different thickness than dielectric layer 221,which adds to design flexibility.

In one embodiment, active trenches 23 and 24 further include aconductive layer 237/238, a conductive region 237/238 or a conductivematerial 237/238 provided along surfaces adjoining dielectric layer222/221 respectively. In one embodiment, conductive material 237/238 canbe a conductive polycrystalline material, such as a doped polysilicon.In some embodiments, active trenches 23 and 24 can have a width in arange from approximately 0.1 microns to approximately 0.6 microns. Inone embodiment, active trenches 23 and 24 can have a width ofapproximately 0.3 microns. In accordance with the present embodiment,device 10 can have an active trench 23 width to termination trench 21width ratio less in a range from approximately 0.005 to approximately0.125. In other embodiments, device 10 can have an active trench 23width to termination trench 21 width ratio less than approximately 0.03.

In accordance with the present embodiment, depth 216 of terminationtrench 21 and depth 224 of active trenches 24 are greater than depth 226of active trenches 23 so that a trench depth difference 236 (that is,depth 216 minus depth 226 and/or depth 224 minus depth 226) greater thanzero exists between termination trench 21 and active trenches 23 andbetween active trenches 24 and active trenches 23.

Device 10 further includes conductive layer 26, conductive region orregions 26, or conductive material 26 disposed adjoining portions ofmajor surface 18. In some embodiments, conductive material 26 also canbe disposed adjoining upper surface portions of conductive material237/238 and upper surface portions of conductive spacers 217. Inaccordance with the present embodiment, conductive material 26 comprisesa material configured to provide a Schottky barrier with region ofsemiconductor material 11 or semiconductor layer 14. Such materials caninclude platinum, nickel-platinum (with various platinum atomic weightpercentages, for example, from approximately 1% to approximately 80%,with 5% being selected in some embodiments), titanium,titanium-tungsten, chromium, and/or other materials capable of forming aSchottky barrier as known to those of ordinary skill in the art.

In other embodiments, device 10 may also include a doped region 31,which can be either n-type or p-type provided adjacent major surface 18and adjacent conductive material 26. In one embodiment, doped region 31can be configured to adjust the barrier height between region ofsemiconductor material 11 and conductive material 26 in accordance withdesired device characteristics. Doped region 31 can be provided usingion implantation and anneal techniques, epitaxial growth techniques, orother doping techniques as known to those of ordinary skill in the art.In one embodiment, doped region 31 extends into region of semiconductormaterial 11 less than approximately 1.0 micron. In other embodiments,doped region 31 can be provided in only some mesa regions and not inothers to provide different Schottky barrier heights between mesaregions.

In some embodiments, device 10 may include a deeper doped region (notillustrated) provided below doped region 31 to provide for conductiontuning of the device. This may also be done by providing, for example, agraded dopant profile within semiconductor layer 14 by using gradedepitaxial growth techniques or by using multiple ion implants.

A conductive layer 44 can be formed overlying major surface 18, and aconductive layer 46 can be formed overlying major surface 19. Conductivelayers 44 and 46 can be configured to provide electrical connectionbetween device 10 and a next level of assembly. In accordance with thepresent embodiment, conductive layer 44 is electrically connected toconductive material 26. In one embodiment, conductive layer 44 can betitanium/titanium-nitride/aluminum-copper or other related or equivalentmaterials known by one of ordinary skill in the art and is configured asfirst current carrying electrode or terminal 440 or an anode electrode440 for device 10. In one embodiment, conductive layer 46 can be asolderable metal structure such as titanium-nickel-silver,chromium-nickel-gold, or other related or equivalent materials known byone of ordinary skill in the art. In the embodiment illustrated,conductive layer 46 provides a second current carrying electrode orterminal 460 or a cathode electrode 460 for device 10.

In accordance with the present embodiment, active trenches 23 and 24 areconfigured to have a reduced width compared to related devices in orderto reduce the area occupied by the trenches in the active area. Thisreduced width increases their aspect ratio (that is, depth to widthratio), which results in termination trench 21 being formed to a greaterdepth than active trenches 23 during their single formation step toprovide trench depth difference 236. In accordance with the presentembodiment as will be described in more detail hereinafter, activetrenches 24 can be formed in a separate masking and etching step so thatactive trenches 24 can have substantially the same depth as terminationtrench 21.

Evaluation studies were done on device 10 with active trenches 23 and 24to evaluate breakdown voltage VR (volts), leakage current IR (Amps) andforward voltage drop VF (volts) compared to a standard planar Schottkydevice and a trench Schottky rectifier where all of active trenches wereshallower than termination trench 21. The same device package and diesize were used for the evaluation. For device 10, the resistivity ofsemiconductor layer 14 was 0.12 ohm-cm, the trench depth difference 236was 1.2 microns between active trenches 23 and termination trench 21,and the depths of termination trench 21 and active trenches 24 weresubstantially the same. In one of the trench Schottky rectifier devices,the trench depth difference between all of the active trenches and thetermination trench was 1.2 microns and the resistivity of semiconductorlayer proximate to the Schottky barrier was 0.18 ohm-cm (Device A). Forthe other trench Schottky rectifier device, the trench depth differencebetween all of the active trenches and the termination trench was 1.2microns, and the resistivity of semiconductor layer proximate to theSchottky barrier was 0.12 ohm-cm (Device B). For the planar Schottkyrectifier, the resistivity of the semiconductor layer proximate to theSchottky barrier was 0.7 ohm-cm (Planar Device).

The evaluation studies showed that the device 10 had a breakdown voltageof 53.7 volts, Device A had a breakdown voltage of 52 volts, Device Bhad a breakdown voltage of 49.2 volts, and the Planar Device had abreakdown voltage of 50 volts. Also, device 10 had a forward voltage at0.5 Amps of 0.47 volts, Device A had a forward voltage at 0.5 Amps of0.6 volts, Device B had a forward voltage at 0.5 Amps of 0.46 volts, andthe Planar Device had a forward voltage at 0.5 Amps of 0.78 volts.Additionally, device 10 had a forward voltage at 1.0 Amp of 0.66 volts,Device A had a forward voltage at 1.0 Amp of 0.76 volts, Device B had aforward voltage at 1.0 Amp of 0.65 volts, and the Planar Device had anunmeasurable forward voltage at 1.0 Amp. In addition, device 10 had aleakage current IR at 40 volts of 1.1 micro-Amps, Device A had a leakagecurrent IR at 40 volts of 0.18 micro-Amps, Device B had a leakagecurrent IR at 40 volts of 2.9 micro-Amps, and the Planar Device had aleakage current IR at 40 volts of 7.0 micro-Amps. Finally, device 10 andDevice B showed the best power dissipation of about 16 milli-Watts,Device A had a power dissipation of about 21 milli-Watts, and the PlanarDevice had a power dissipation of about 27.5 milli-watts. Based on theforegoing data device 10 exhibited the best overall performance. Thisdata is further summarized in Table 1.

TABLE 1 Summary Data Device VR VF @ 0.5 Amps VF @ 1 Amp IR @ 40 VoltsPower Dissipation Device 10 53.7 Volts 0.47 Volts 0.66 Volts 1.1micro-Amps 16 milli-Watts Device A 52 Volts 0.6 Volts 0.76 Volts 0.18micro-Amps 21 milli-Watts Device B 49.2 Volts 0.46 Volts 0.65 Volts 2.9micro-Amps 16 milli-Watts Planar Device 50 Volts 0.78 Volts N/A 7.0micro-Amps 27.5 milli-Watts

In another evaluation study, data for two configurations of a trenchSchottky rectifier without active trenches 24 and having a trench depthdifference 236 of 1.2 microns and data for two configurations of adevice where the trench depth difference 236 is zero were studied. Inone configuration of both devices, the dopant concentration ofsemiconductor layer 14 was 4.0×10¹⁶ atoms/cm³ and in the otherconfiguration of both devices, the dopant concentration of semiconductorlayer was 1.0×10¹⁶ atoms/cm³. In all devices, the thickness ofsemiconductor layer 14 was 3.5 microns. In related trench Schottkyrectifiers, a dopant concentration of 1.0×10¹⁶ atoms/cm³ is a typicaldopant concentration for a 45 volt device and 4.0×10¹⁶ atoms/cm³ is atypical dopant concentration for a 40 volt device.

The additional evaluation showed that breakdown voltage decreased astrench depth difference 236 changed from zero to 1.2 microns. This isbelieved to be the result of deeper termination trench 21, which mayreduce the supported electric field along lower surface 210 as well asreduction of the electric field along the sidewall surfaces oftermination trench 21. However, it was unexpected to see that althoughbreakdown voltage decreased by approximately 12 volts for the 45 voltmaterial (that is, dopant concentration of 1.0×10¹⁶ atoms/cm³) from 62volts to 50 volts, VR decreased by only approximately 4 volts for the 40volt material (that is, dopant concentration of 4.0×10¹⁶ atoms/cm³) from56 volts to approximately 52 volts.

Based on this unexpected result, the variation in breakdown voltage VRwith trench depth difference 236 using different dopant concentrationsfor semiconductor layer 14 of 3.5 microns in thickness was also studied.This study showed that breakdown voltage VR variation with trench depthdifference 236 decreases with decreasing dopant concentration ofsemiconductor layer 14. At higher dopant concentrations (for example,approximately 6.0×10¹⁶ atoms/cm³), the breakdown voltage unexpectedlyremains substantially unchanged with changes in the trench depthdifference 236. It is believed that this results from, at least in part,a reduced surface field (“RESURF”) effect provided by the configurationof device 10 in accordance with the present embodiment. Also, a chargesharing effect along sidewall surfaces of termination trench 21 isbelieved to contribute to sustaining the breakdown voltage. In oneembodiment, the surfaces of the termination trench adjoiningsemiconductor layer 14 are configured (e.g., shape, dielectricthickness, conductive spacers 217, and/or dopant concentration ofsemiconductor layer 14) to provide a field shaping and/or charge sharingeffect for the semiconductor device. In accordance with the presentembodiment, increasing the dopant concentration of semiconductor layer14 reduces the effect of trench depth difference 236 on breakdownvoltage VR, which also improves overall performance and robustness ofdevice 10.

Further in accordance with the present embodiment, it is believed that,among other things, adding alternate deeper active trenches 24 withdevice 10 provides for a more uniform electric field spreading over theentire device structure. In addition, the deeper active trenches 24provide secondary electric field pinching off between them, which reduceelectric field near the Schottky surface further than a structure wherethe active trenches are all shallower. As discussed previously, theconfiguration of device 10 enables the use of a lower resistivitysemiconductor layer 14 (0.12 ohm-cm), while providing a breakdownvoltage VR of 53.7 V. This is a gain of 4 V in breakdown voltage over astructure where the active trenches are all shallower (about an 8% gainin VR).

In summary, the present embodiment provides several benefits compared toother trench Schottky rectifiers and planar Schottky rectifiersincluding a higher breakdown voltage VR and lower forward voltage VFwith only a slightly higher IR. The structure of device 10 enableshigher dopant concentrations to be used within semiconductor layer 14,which provides, among other things, lower forward voltages and thus,lower power dissipation. This also helps improve other devicecharacteristics, such as UIS and ESD.

In one embodiment, active trenches 23 have a depth 226 in a range fromapproximately 0.5 microns to approximately 10.0 microns withoutdielectric layer 222, and active trenches 24 have a depth 224 in a rangefrom approximately 1.0 micron to approximately 10.0 microns withoutdielectric layer 222. In one embodiment, termination trench 21 has adepth 216 in a range from approximately 1.7 microns to approximately 6.0microns without dielectric layer 212. In some embodiments, semiconductorlayer 14 has a thickness in a range from approximately 1 micron toapproximately 15 microns and dopant concentration in a range fromapproximately 5.0×10¹³ atoms/cm³ to approximately 5.0×10¹⁷ atoms/cm³. Insome embodiments, trench depth difference 236 is in a range greater thanzero to approximately 3.0 microns.

In one embodiment, trench depth difference 236 is less thanapproximately 2.0 microns. In another embodiment, trench depthdifference 236 is in a range greater than zero to approximately 1.0microns. In a further embodiment, trench depth difference 236 is in arange greater than zero to approximately 0.8 microns. In a still furtherembodiment for a 20 volt trench semiconductor device, semiconductorlayer 14 has a thickness from approximately 2.0 microns to approximately2.5 microns, a dopant concentration in a range from approximately2.0×10¹⁶ atoms/cm³ and approximately 8.0×10¹⁶ atoms/cm³, and a trenchdepth difference 236 in a range greater than zero to approximately 2.0microns. In another embodiment for a 30 volt trench semiconductordevice, semiconductor layer 14 has a thickness from approximately 2.4microns to approximately 3.2 microns, a dopant concentration in a rangefrom approximately 1.5×10¹⁶ atoms/cm³ and approximately 7.0×10¹⁶atoms/cm³, and a trench depth difference 236 in a range from greaterthan zero to approximately 1.8 microns. In a further embodiment, for a40 volt trench semiconductor device, semiconductor layer 14 has athickness from approximately 3.0 microns to approximately 4.0 microns, adopant concentration in a range from approximately 1.0×10¹⁶ atoms/cm³and approximately 6.0×10¹⁶ atoms/cm³, and a trench depth difference 236in a range greater than zero to approximately 1.5 microns.

In another embodiment, the active trenches 23 and 24 have a pitch in arange from approximately 0.5 microns to about 4.5 microns. It isunderstood that depending on the desired layout, this includes the pitchbetween an active trench 23 adjacent an active trench 24, an activetrench 23 adjacent another active trench 23, and/or an active trench 24adjacent another active trench 24. It is further understood that in someembodiments, the pitch between adjacent active trenches 23 can bedifferent than the pitch between active trenches 24. In a furtherembodiment, the pitch can be in a range from approximately 0.6 micronsto approximately 0.75 microns. In still further embodiment, the pitchcan be in a range from approximately 0.85 microns to about 0.95 microns.In another embodiment, the pitch can be in a range from approximately1.1 microns to approximately 1.25 microns. In a further embodiment, thespacing between adjacent active trenches 23 and 24 can be in a rangefrom approximately 0.4 microns to approximately 4.0 microns.

Turning now to FIGS. 2-14, a method for forming device 10 in accordancewith one embodiment is described. In FIG. 2, which is a partialcross-section view of device 10 at an early step in fabrication, regionof semiconductor material 11 is provided having substrate 12 with majorsurface 19′ and semiconductor layer 14 with major surface 18. In oneembodiment, substrate 12 can be an n-type silicon substrate having aresistivity ranging from about 0.001 ohm-cm to about 0.005 ohm-cm andcan be doped with arsenic. In one embodiment, semiconductor layer 14 isprovided using epitaxial growth techniques and can be provided having athickness 51 in a range from approximately 1.0 microns to approximately15 microns. In one embodiment, semiconductor layer 14 can have dopantconcentration in one of the ranges described previously. In oneembodiment semiconductor layer 14 is n-type and doped with phosphorous.In some embodiments, semiconductor layer 14 has a substantially uniformdopant profile along or over thickness 51. In other embodiments,semiconductor layer 14 has a non-uniform dopant profile along or overthickness 51. For example, semiconductor layer 14 can have a gradeddopant profile where the dopant concentration can decrease from majorsurface 18 over thickness 51 towards substrate 12. In another example,the dopant concentration can increase over thickness 51 from majorsurface 18 towards substrate 12. In yet another example, the dopantconcentration can first increase and then decrease over thickness 51from major surface 18 towards substrate 12. In one embodiment, a layer61 can be formed on major surface 18. In one embodiment, layer 61 can bea dielectric material, such as an oxide or another material configuredfor providing a hard mask. In one embodiment, layer 61 is a thermaloxide having a thickness in a range from about 0.1 microns to about 0.5microns. A masking layer 62 is then formed on layer 61. In oneembodiment, masking layer 62 can be a photoresist layer patterned toprovide an opening 610 configured in a desired pattern for terminationtrench 21, and to provide openings 620 configured in a desired patternfor active trenches 23.

FIG. 3 illustrates a partial cross-sectional view of device 10 afteradditional processing. A removal step, such as an etch step, can be usedto provide openings 610′ and 620′ in layer 61. Masking layer 62 can thenbe removed. The foregoing steps can provide opening 610′ having a width74 in a range from approximately 4 microns to approximately 20 microns,and can provide openings 620′ having a width 72 of approximately 0.1microns to approximately 0.5 microns. In one embodiment, width 72 isapproximately 0.3 microns.

FIG. 4 illustrates a partial cross-sectional view of device 10 afteradditional processing. In accordance with the present embodiment, asingle removal step is used to form both termination trench 21 andactive trenches 23, which have different depths. In one embodiment,termination trench 21 and active trenches 23 can be etched using plasmaetching techniques with a fluorocarbon chemistry or a fluorinatedchemistry (for example, SF₆/O₂) or other chemistries or removaltechniques as known to those of ordinary skill in the art. In oneembodiment, active trenches 23 have a depth 226 in a range fromapproximately 0.5 microns to approximately 4.0 microns. In oneembodiment, termination trench 21 has a depth 216 in a range fromapproximately 1.0 micron to approximately 10.0 microns. In accordancewith the present embodiment, active trenches 23 are provided with adepth 226 and termination trench is provided with a depth 216 greaterthan depth 226. This difference provides trench depth difference 236.

FIG. 5 illustrates a partial cross-sectional view of device 10 afterfurther processing. In one embodiment, a layer 200 is formed alongsurfaces of termination trench 21, surfaces of active trenches 23, andmajor surface 18. In one embodiment, layer 200 is a dielectric material,such as an oxide, a nitride, tantalum pentoxide, titanium dioxide,barium strontium titanate, high k dielectric materials, combinationsthereof, or other related or equivalent materials known by one ofordinary skill in the art. In one embodiment, layer 200 is a thermaloxide having a thickness in a range from approximately 0.05 microns toapproximately 0.6 microns. In accordance with the present embodiment,layer 200 has a selected thickness that leaves a gap 81 or void 81between adjacent surfaces of layer 200 within active trenches 23 asgenerally illustrated in FIG. 5. In other embodiments, the sidewallsurfaces of termination trench 21 can be sloped to provide further fieldshaping effects.

In subsequent steps, a conductive layer is provided on layer 200 andthen partially removed or etched back to provide conductive spacers 217within termination trench 21 and conductive layers 237′ within activetrenches 23 as illustrated in FIG. 6. In one embodiment, the conductivelayer can be a polysilicon layer doped with an n-type dopant, such asphosphorous. In one embodiment, the dopant concentration can beapproximately 2.0×10¹⁹ atoms/cm³. In one embodiment, conductive spacers217 are provided having a thickness of approximately 1.6 microns.

FIG. 7 illustrates a partial cross-sectional view of device 10 afteradditional processing. In one embodiment, a layer 77 of material isprovided adjacent layer 200 and spacers 217. In one embodiment, layer 77is a dielectric material, such a silicon nitride or another oxidationresistant material. In one embodiment, layer 77 has a thickness fromapproximately 0.15 microns to approximately 0.3 microns. Next, a maskinglayer 67 is provided on layer 77 and patterned to provide openings 624′for active trenches 24. In one embodiment, masking layer 67 can be aphotoresist layer. In one embodiment, openings 624′ having a width 75 ofapproximately 0.1 microns to approximately 0.6 microns. In oneembodiment, width 75 is approximately 0.3 microns.

FIG. 8 illustrates a partial cross-sectional view of device 10 afterstill further processing. In one embodiment, one or more removal stepsare used to remove portions of layer 77 and layer 200 adjacent openings624′ to provide openings 624. Masking layer 67 can then be removed.Next, active trenches 24 can be etched using plasma etching techniqueswith a fluorocarbon chemistry or a fluorinated chemistry (for example,SF₆/O₂) or other chemistries or removal techniques as known to those ofordinary skill in the art. In one embodiment, active trenches 24 have adepth 224 in a range from approximately 1.0 microns to approximately10.0 microns. In one embodiment, active trenches 23 are provided with adepth 226 and active trenches 24 are provided with a depth 224 greaterthan depth 226. In one embodiment, this difference can be substantiallyequal to trench depth difference 236. In one embodiment, device 10 canhave a spacing 73 in a range from approximately 0.4 microns toapproximately 3.5 microns, and a pitch 71 in a range from approximately0.5 microns to about 4.5 microns. In one embodiment, active trenches 24have a width 75. In accordance with the present embodiment, width 75 canbe the same or different to width 72 of active trenches 23, which addsto design flexibility. Next, a layer 201 of material can be providedwithin active trenches 24 as illustrated in FIG. 9. In one embodiment,layer 201 can be the same or a similar material to layer 200. In oneembodiment, layer 201 has a thickness in a range from approximately 0.05microns to approximately 0.2 microns. In some embodiments, layer 201 hasa similar thickness to layer 200. In other embodiments, layer 201 can bethicker or thinner than layer 200, which adds to design flexibility. Insubsequent step, layer 77 can be removed.

In subsequent steps, another conductive layer is provided on layer 201and then partially removed or etched back to provide conductive layers238′ within active trenches 24 as illustrated in FIG. 10. In oneembodiment, the conductive layer can be a polysilicon layer doped withan n-type dopant, such as phosphorous. In one embodiment, the dopantconcentration can be approximately 2.0×10¹⁹ atoms/cm³.

FIG. 11 illustrates a partial cross-sectional view of device 10 afterfurther processing. In one embodiment, a layer of material is providedadjacent major surface 18. In accordance with the present embodiment,the layer of material can be a TEOS oxide deposited using a PECVDprocess or an LPCVD process, and can have thickness in a range fromapproximately 0.35 microns to approximately 0.7 microns. Next, a maskingstep and removal step can be used to leave a portion of the layer ofmaterial within termination trench 21 to provide dielectric layer 219.The masking and removal steps can further remove portions of layer 200from the active region of device 10 to expose portions of major surface18. This provides dielectric layer 212 within termination trench 21,dielectric layers 222 within active trenches 23, and dielectric layers221 within active trenches 24. The masking and removal steps can alsoremove portions of conductive layers 237′ to provide conductive layers237 and portions of conductive layers 238′ to provide conductive layers238. In an optional step, doped region 31 can be provided at this stageof fabrication, and can be formed using ion implantation or other dopingtechniques as known to those of ordinary skill in the art. Alsoadditional n-type dopant can be added to semiconductor layer 14 betweenactive trenches 23 to provide semiconductor layer 14 with a modifieddopant profile, such as a non-uniform dopant profile. This can providefor conduction adjustment in accordance with desired performancerequirements.

FIG. 12 illustrates a partial cross-sectional view of device 10 afterstill further processing. In one embodiment, the exposed portions ofmajor surface 18 are cleaned using, for example, a hydrofluoric acidprocess. Next, conductive layer 26′ is provided on device 10 proximateto major surface 18. In accordance with the present embodiment,conductive layer 26′ comprises a material configured to provide aSchottky barrier with semiconductor layer 14. Such materials can includeplatinum, nickel-platinum, titanium, titanium-tungsten, chromium, and/orother materials capable of forming a Schottky barrier as known to thoseof ordinary skill in the art. In some embodiments, conductive layer 26′can be heat treated or annealed to provide silicide regions and thenportions of conductive layer 26′ are removed to provide conductivematerial 26 as illustrated in FIG. 13. In accordance with the presentembodiment, a portion of conductive material 26 is provided onconductive spacer 217 as generally illustrated in FIG. 13. This providesfor improved electrical contact between conductive spacer 217 andconductive layer 44.

FIG. 14 illustrates a partial cross-sectional view of device 10 afteradditional processing. In one embodiment, a conductive layer is providedon device 10 proximate to major surface and then patterned using amasking layer 130. This provides conductive layer 44. In one embodiment,conductive layer 44 can be titanium/titanium-nitride/aluminum-copper orother related or equivalent materials known by one of ordinary skill inthe art and is configured as first current carrying electrode orterminal 440 or an anode electrode 440 for device 10. Next, substrate 12can be thinned to decrease its thickness using, for example, a grindingprocess to provide major surface 19. Conductive layer 46 can then beprovided on major surface 19 as described and illustrated in FIG. 1.

In a further embodiment, the method described in FIGS. 2-14 can be usedto manufacture a semiconductor device having high aspect ratio activetrenches or active trench widths less than approximately 0.5 microns forsome embodiments or less than approximately 0.3 microns for otherembodiments, where it is desired that all of the active trenches haveapproximately the same trench depths as the termination trench. Statedanother way, for a trench Schottky rectifier device having terminationtrench 21 as illustrated in FIG. 1 and only active trenches 24 (that is,active trenches 23 replaced with active trenches 24), the method woulduse one masking step as illustrated in FIGS. 2-3 to form opening 610′and subsequently termination trench 21, and use another masking step asillustrated in FIGS. 7-9 to form openings 624′ and subsequently allactive trenches 24 having depths similar to the depth of terminationtrench 21. This method could be used, for example, to provide a trenchSchottky device embodiment with high aspect ratio active trenches 24having trench depth 224 similar to trench depth 216 of terminationtrench 21 without active trenches 23.

FIG. 15 illustrates a partial cross-sectional view of an electronicdevice 100, a semiconductor device 100, Schottky diode device 100, ortrench Schottky rectifier 100 in accordance with another embodiment.Device 100 is similar to device 10 and only the differences between thetwo devices are described hereinafter. Specifically, in device 100 depth216 of trench 21, depth 226 of active trenches 23, and depth 224 ofactive trenches are each different from each other. In one embodiment,depth 216 is greater than depths 226 and 224, and depth 224 is greaterthan depth 226. In one embodiment, the width of active trenches 24 isgreater than the width of the active trenches 23. In another embodiment,the width of active trenches 24 can be smaller than the width of activetrenches 23.

FIG. 16 illustrates a partial cross-sectional view of an electronicdevice 200, a semiconductor device 200, Schottky diode device 200, ortrench Schottky rectifier 200 in accordance with another embodiment.Device 200 is similar to devices 10 and 100 and only the differencesbetween the three devices are described hereinafter. Specifically, indevice 200 depth 216 of trench 21, depth 226 of active trenches 23, anddepth 224 of active trenches are each different from each other. In oneembodiment, depth 216 is greater than depth 226, and depth 224 isgreater than depths 216 and 226.

In some embodiments, devices 10, 100, and 200 can have at least oneactive trench 24 disposed between a pair of active trenches 23. In otherembodiments, a pair of active trenches 24 can be disposed between a pairof active trenches 23. In still further embodiments, at least two activetrenches 23 separate each active trench 24. One of ordinary skill in theart will appreciate that other combinations active trenches 23 andactive trenches 24 are possible as well. Additionally, in someembodiments, the width of active trenches 24 is greater than the widthof the active trenches 23 (for example, as illustrated in FIG. 16). Inother embodiments, the width of active trenches 24 can be smaller thanthe width of active trenches 23 (for example, as illustrated in FIG.15).

From all of the foregoing, one skilled in the art can determine that,according to one embodiment, a semiconductor device (for example,elements 10, 100, 200) includes a region of semiconductor material (forexample, elements 11, 12, 14) having a first conductivity type and amajor surface (for example, element 18). A first active trench (forexample, element 23) extends from a first portion of the major surfaceinto the region of semiconductor material to a first depth (for example,element 226), wherein the first active trench has a first width (forexample, element 72). A second active trench extends from a secondportion of the major surface into the region of semiconductor materialto a second depth (for example, 224), wherein the second active trenchhas a second width (for example, element 75), and wherein the seconddepth is greater than the first depth. A first conductive material (forexample, element 237) is within the first active trench and separatedfrom the region of semiconductor material by a first dielectric region(for example, element 222). A second conductive material (for example,element 238) within the second active trench and separated from theregion of semiconductor material by a second dielectric region (forexample, element 221). A third conductive material (for example, element26) adjoins a third portion of the major surface, wherein the thirdconductive material is configured to provide a Schottky barrier.

From all of the foregoing, one skilled in the art can determine that,according to another embodiment, the semiconductor device can furtherinclude a third trench (for example, element 21) extending from a fourthportion of the major surface into the region of semiconductor material,wherein at least a portion of third trench can extend to a third depth(for example, element 216), the third trench can have a third width (forexample, element 74), the third depth can be greater than the firstdepth (for example, element 236), and the third width can be greaterthan the first width and the second width. In a further embodiment, thethird depth and the second depth can be substantially equal. In a stillfurther embodiment, the second depth can be greater than the thirddepth. In another embodiment, the third depth can be greater than thefirst depth in a range greater than zero to approximately 3.0 microns.In a further embodiment, the third depth can be greater than the firstdepth in a range greater than zero to approximately 2.0 microns. In astill further embodiment, the third depth can be greater than the firstdepth in a range greater than zero to approximately 1.5 microns. Inanother embodiment, the second width can be different than the firstwidth. In a further embodiment, the semiconductor device can have afirst width to third width ratio in a range from approximately 0.005 toapproximately 0.125. In a still further embodiment, the semiconductordevice can have a first width to third width ratio is less than or equalto approximately 0.03. In another embodiment, the first dielectricregion and the second dielectric region have different thicknesses.

From all of the foregoing, one skilled in the art can determine that,according to another embodiment, the region of semiconductor materialcomprises a semiconductor layer (for example, element 14) adjoining asemiconductor substrate (for example, element 12); the semiconductorlayer defines the major surface; and the semiconductor layer has a firstdopant concentration and the semiconductor substrate has a second dopantconcentration greater than the first dopant concentration. In a furtherembodiment, the third depth is greater than the first depth in a rangegreater than zero to approximately 3.0 microns. In a still furtherembodiment, the semiconductor layer has a thickness from approximately1.0 micron to approximately 15 microns. In another embodiment, the firstdopant concentration is in a range from approximately 5.0×10¹³ atoms/cm³and approximately 5.0×10¹⁷ atoms/cm³. In a further embodiment, thesemiconductor layer can have a thickness from approximately 1.0 micronsto approximately 2.5 microns; the first dopant concentration can be in arange from approximately 2.0×10¹⁶ atoms/cm³ and approximately 8.0×10¹⁶atoms/cm³; and the third depth can be greater than the first depth in arange greater than zero to approximately 2.0 microns. In a still furtherembodiment, the semiconductor layer can have a thickness fromapproximately 2.4 microns to approximately 3.2 microns; the first dopantconcentration is in a range from approximately 1.5×10¹⁶ atoms/cm³ andapproximately 7.0×10¹⁶ atoms/cm³; and the third depth can be greaterthan the first depth in a range greater than zero to approximately 1.8microns. In another embodiment, the semiconductor layer can have athickness from approximately 3.0 microns to approximately 6.0 microns;the first dopant concentration can be in a range from approximately1.0×10¹⁶ atoms/cm³ and approximately 6.0×10¹⁶ atoms/cm³; and the firstdepth can be greater than the second depth in a range greater than zeroto approximately 1.5 microns.

From all of the foregoing, one skilled in the art can determine that,according to another embodiment, surfaces of the termination trenchadjoining the semiconductor layer are configured to provide a fieldshaping effect for the semiconductor device. In a further embodiment,the semiconductor layer can have a non-uniform dopant profile. In stillfurther embodiment, the first dielectric region has a thickness in arange from approximately 0.05 microns to approximately 0.6 microns. In afurther embodiment, a doped layer (for example, element 31) adjoins thethird portion of the major surface adjacent to the second conductivematerial. In a still further embodiment, the first width and the secondwidth can be approximately the same.

From all of the foregoing, one skilled in the art can determine that,according to a further embodiment, a semiconductor device (for example,elements 10, 100, 200) includes a region of semiconductor material (forexample, element 11) comprising a semiconductor layer (for example,element 14) adjoining a semiconductor substrate (for example, element12), the semiconductor layer defining a major surface (for example,element 18), wherein the semiconductor layer has a first dopantconcentration and the semiconductor substrate has a second dopantconcentration greater than the first dopant concentration. A firsttrench (for example, element 21) extends from a first portion of themajor surface into the region of semiconductor material, wherein thefirst trench extends to a first depth (for example, element 216), andwherein the first trench has a first width (for example, element 74). Asecond trench (for example, element 23) extends from a second portion ofthe major surface into the region of semiconductor material to a seconddepth (for example, element 226), wherein the second trench has a secondwidth (for example, element 72) less than the first width, and whereinthe first depth is greater than the second depth to define a trenchdepth difference (for example, element 236). A third trench (forexample, element 24) extends from a third portion of the major surfaceinto the region of semiconductor material to a third depth (for example,element 224) greater than the second depth, wherein the third trench hasa third width (for example, element 75). A first conductive material(for example, element 237) is within the second trench and separatedfrom the region of semiconductor material by a first dielectric region(for example, element 222). A second conductive material (for example,element 26) adjoins a fourth portion of the major surface, wherein thesecond conductive material is configured to provide a Schottky barrier.

From all of the foregoing, one skilled in the art can determine thataccording to another embodiment, the trench depth difference can begreater than zero but less than approximately 3.0 microns. In a furtherembodiment, the semiconductor layer can have a thickness fromapproximately 1.0 micron to approximately 15 microns. In a still furtherembodiment, the first dopant concentration can be in a range fromapproximately 5.0×10¹³ atoms/cm³ and approximately 5.0×10¹⁷ atoms/cm³.In another embodiment, the first trench can be configured as atermination trench. In a further embodiment, the second trench and thethird trench can be configured as active trenches. In a still furtherembodiment, the second width and the third width are different. Inanother embodiment, the first depth, the second depth, and the thirddepth are different from each other.

From all of the foregoing, one skilled in the art can determine thataccording to another embodiment, a method of forming Schottkysemiconductor device (for example, elements 10, 100, 200) includesproviding a region of semiconductor material (for example, element 11)comprising a semiconductor layer (for example, element 14) adjoining asemiconductor substrate (for example, element 12), the semiconductorlayer defining a major surface (for example, element 18), wherein thesemiconductor layer has a first dopant concentration and thesemiconductor substrate has a second dopant concentration greater thanthe first dopant concentration. The method includes, providing a firsttrench (for example, element 21) extending from a first portion of themajor surface into the region of semiconductor material, wherein thefirst trench extends to a first depth (for example, element 216), andwherein the first trench has a first width (for example, element 74).The method includes providing a first active trench (for example element23) extending from a second portion of the major surface into the regionof semiconductor material to a second depth (for example, element 226),wherein the first active trench has a second width (for example, element72) less than the first width. The method includes providing a secondactive trench (for example, element 24) extending from a third portionof the major surface into the region of semiconductor material to athird depth (for example, element 224), wherein the second active trenchhas a third width (for example, element 75) less than the first width.The method includes providing a conductive material (for example,element 26) adjoining a fourth portion of the major surface, wherein theconductive material is configured to provide a Schottky barrier.

From all of the foregoing, one skilled in the art can determine thataccording to another embodiment, providing the second active trenchincludes providing the third depth greater than the second depth. In afurther embodiment, providing the first trench and providing the firstactive trench comprises forming the first trench and the first activetrench in a single removal step, wherein the first depth is greater thanthe second depth to provide a trench depth difference; and the trenchdepth difference is greater than zero and less than approximately 3.0microns. In a still further embodiment, providing the first trench andproviding the first active trench includes providing a first width tothird width ratio less than or equal to approximately 0.03, and whereinthe first depth, the second depth, and the third depth are different. Inanother embodiment, wherein providing the first trench and providing thefirst active trench includes providing a first width to third widthratio less than or equal to approximately 0.03, and wherein providingthe first active trench and providing the second active trench comprisesforming the first active trench and the second active trench in a singleremoval step, and wherein the first depth, the second depth, and thethird depth are substantially equal. In a further embodiment, the methodcan further include providing a first dielectric structure in the firstactive trench; and providing a second dielectric structure in the secondactive trench. In still further embodiment, providing the seconddielectric structure includes providing the second dielectric structurehaving a different thickness than that of the first dielectricstructure.

In view of all of the above, it is evident that a novel structure andmethod of making the structure are disclosed. Included, among otherfeatures, is a trench Schottky rectifier device having a terminationtrench, first active trenches, and second active trenches. Thetermination trench and some of the first active trenches have differentdepths to provide a selected trench depth difference. The second activetrenches are provided with substantially the same depth as thetermination trench. The trench depth difference in combination with oneor more of first active trench width to termination width ratio, layerdopant concentration, and/or dopant profile of the semiconductor layer,and layer thickness provide a structure having low leakage, low forwarddrop, fast switching and soft recovery. This provides a needed solutionto industry demands for lower power dissipation, higher power density,improved ESD characteristics, improved UIS performance, and improvedIFSM performance among others. Additionally, the method provides thetrench depth difference in a single masking step, which provides a costeffective solution. Moreover, the deeper second active trenches providea higher breakdown voltage compared to related devices. Finally, themethod enables a trench Schottky rectifier having high aspect ratioactive trenches that have the same depth as wider termination trenchstructures.

While the subject matter of the invention is described with specificpreferred embodiments and example embodiments, the foregoing drawingsand descriptions thereof depict only typical embodiments of the subjectmatter, and are not therefore to be considered limiting of its scope. Itis evident that many alternatives and variations will be apparent tothose skilled in the art.

As the claims hereinafter reflect, inventive aspects may lie in lessthan all features of a single foregoing disclosed embodiment. Thus, thehereinafter expressed claims are hereby expressly incorporated into thisDetailed Description of the Drawings, with each claim standing on itsown as a separate embodiment of the invention. Furthermore, while someembodiments described herein include some but not other featuresincluded in other embodiments, combinations of features of differentembodiments are meant to be within the scope of the invention and meantto form different embodiments as would be understood by those skilled inthe art.

What is claimed is:
 1. A method of forming a semiconductor device,comprising: providing a region of semiconductor material comprising amajor surface; providing a termination trench extending from a firstportion of the major surface into the region of semiconductor materialto a first depth, wherein the termination trench has a first width;providing a first active trench extending from a second portion of themajor surface into the region of semiconductor material to a seconddepth, wherein the first active trench has a second width less than thefirst width; providing a second active trench extending from a thirdportion of the major surface into the region of semiconductor materialto a third depth, wherein: the second active trench has a third widthless than the first width, the third depth is greater than the seconddepth, and the first active trench is interposed between the terminationtrench and the second active trench in a cross-sectional view; providinga first conductive material adjoining a fourth portion of the majorsurface, wherein the first conductive material is configured to providea Schottky barrier; and providing a second conductive material in thefirst active trench separated from the region of semiconductor materialby a first dielectric structure; and providing a third conductivematerial in the second active trench separated from the region ofsemiconductor material by a second dielectric structure.
 2. The methodof claim 1, wherein: providing the termination trench and providing thefirst active trench comprises forming the termination trench and thefirst active trench in a single removal step, wherein: the first depthis greater than the second depth to provide a trench depth difference;and the trench depth difference is greater than zero and less thanapproximately 3.0 microns.
 3. The method of claim 1, wherein: providingthe termination trench and providing the first active trench includesproviding a first width to third width ratio less than or equal toapproximately 0.03.
 4. The method of claim 1, wherein: providing thetermination trench comprises forming the termination trench at an edgeof the semiconductor device such that the termination trench is anoutermost trench for the semiconductor device.
 5. The method of claim 1,wherein: providing the second dielectric structure includes providingthe second dielectric structure having a different thickness than thatof the first dielectric structure.
 6. A method of forming asemiconductor device comprising: providing a region of semiconductormaterial having a first conductivity type and a major surface; providinga termination trench extending from a first portion of the major surfaceinto the region of semiconductor material to a first depth, thetermination trench having a first width, wherein the termination trenchis disposed at an edge of the semiconductor device such that thetermination trench is an outermost trench for the semiconductor device;providing a first active trench extending from a second portion of themajor surface into the region of semiconductor material to a seconddepth, wherein the first active trench has a second width; providing asecond active trench extending from a third portion of the major surfaceinto the region of semiconductor material to a third depth, wherein thesecond active trench has a third width, and wherein the third depth isgreater than the second depth, wherein: the termination trench islaterally interposed between the edge and the first active trench andthe second active trench; the first active trench is interposed betweenthe second active trench and the termination trench; the first depth isgreater than the second depth; and the first width is greater than thesecond width and the third width; providing a first conductive materialwithin the first active trench and separated from the region ofsemiconductor material by a first dielectric region; providing a secondconductive material within the second active trench and separated fromthe region of semiconductor material by a second dielectric region; andproviding a third conductive material adjoining a fourth portion of themajor surface, wherein the third conductive material is configured toprovide a Schottky barrier.
 7. The method of claim 6, wherein: providingthe termination trench and providing the first active trench comprisesproviding the termination trench and the first active trench in a singleremoval step.
 8. The method of claim 6, further comprising: providing aconductive spacer disposed along a sidewall of the termination trenchand separated from the region of semiconductor material by a thirddielectric region that adjoins the sidewall surface and a lower surfaceof the termination trench; and providing a dielectric layer disposedadjacent to the conductive spacer within the termination trench suchthat the conductive spacer is laterally interposed between thedielectric layer and the third dielectric region, wherein: the firstdepth is greater than the second depth in a range greater than zero toapproximately 3.0 microns; and the third conductive material physicallycontacts the conductive spacer.
 9. The method of claim 6, wherein:providing the first active trench comprises providing a plurality offirst active trenches each having the second depth; providing the secondactive trench comprises providing a plurality of second active trencheswhere at least two of the second active trenches have the third depth;one of the plurality of first active trenches is interposed between anoutermost one of the plurality of second active trenches and thetermination trench in a cross-sectional view; and another one of theplurality of first active trenches is interposed between a pair ofsecond active trenches in the cross-sectional view.
 10. The method ofclaim 6, further comprising: providing a third active trench extendingfrom a fifth portion of the major surface to the second depth; andproviding a fourth conductive material within the third active trenchand separated from the region of semiconductor material by a thirddielectric region; wherein: the third width is different than the secondwidth; and the second active trench is interposed between the firstactive trench and the third active trench in a cross-sectional view suchthat the second active trench is closer to the edge of the semiconductordevice than the third active trench.
 11. The method of claim 6, wherein:providing the termination trench and providing the first active trenchcomprises providing a second width to first width ratio in a range fromapproximately 0.005 to approximately 0.125.
 12. The method of claim 6,wherein: providing the region of semiconductor material comprisesproviding a semiconductor substrate having a semiconductor layeradjoining a surface of the semiconductor substrate, wherein thesemiconductor layer has a non-uniform dopant profile.
 13. The method ofclaim 6 further comprising: providing a doped layer adjoining the fourthportion of the major surface proximate to the third conductive material,wherein the doped layer has a fourth depth less than the second depth.14. A method of forming a semiconductor device, comprising: providing aregion of semiconductor material comprising a semiconductor layeradjoining a semiconductor substrate, the semiconductor layer defining amajor surface, wherein the semiconductor layer has a first dopantconcentration and the semiconductor substrate has a second dopantconcentration different than the first dopant concentration; providing atermination trench extending from a first portion of the major surfaceinto the region of semiconductor material, wherein: the terminationtrench extends to a first depth; the termination trench has a firstwidth; the termination trench is disposed at an edge portion of thesemiconductor device such that the termination trench is an outermosttrench for the semiconductor device; providing first active trenchesextending from second portions of the major surface into the region ofsemiconductor material to a second depth, wherein: the first activetrenches have a second width less than the first width; and the firstdepth is greater than the second depth to define a trench depthdifference; providing second active trenches extending from thirdportions of the major surface into the region of semiconductor materialto a third depth greater than the second depth, wherein the secondactive trenches have a third width; providing a first conductivematerial within the first active trenches and the second active trenchesand each separated from the region of semiconductor material by a firstdielectric region; and providing a second conductive material adjoininga fourth portion of the major surface, wherein the second conductivematerial is configured to provide a Schottky barrier, wherein: the firstactive trenches and the second active trenches are provided in analternating configuration such that at least one of the first activetrenches is interposed between a pair of second active trenches in across-sectional view.
 15. The method of claim 14, wherein: providing thetermination trench and providing the first active trenches comprisesforming the termination trench and the first active trenches in a singleremoval step.
 16. The method of claim 15, wherein providing the firstactive trenches comprises: providing the trench depth difference greaterthan zero but less than approximately 3.0 microns; and providing anotherfirst active trench disposed as a closest active trench to thetermination trench and further interposed between the termination trenchand one of the second active trenches in the cross-sectional view. 17.The method of claim 15, wherein: providing the termination trench andproviding the first active trenches comprises providing a second widthto first width ratio less than or equal to approximately 0.03.
 18. Themethod of claim 15, wherein: providing the first active trenches andproviding the second active trenches comprises providing the secondwidth different than the third width.
 19. The method of claim 15,wherein: the first depth, the second depth, and the third depth are eachdifferent depths.